DRAM cells

ABSTRACT

The invention includes a method of forming a rugged semiconductor-containing surface. A first semiconductor layer is formed over a substrate, and a second semiconductor layer is formed over the first semiconductor layer. Subsequently, a third semiconductor layer is formed over the second semiconductor layer, and semiconductor-containing seeds are formed over the third semiconductor layer. The seeds are annealed to form the rugged semiconductor-containing surface. The first, second and third semiconductor layers are part of a common stack, and can be together utilized within a storage node of a capacitor construction. The invention also includes semiconductor structures comprising rugged surfaces. The rugged surfaces can be, for example, rugged silicon.

TECHNICAL FIELD

The invention pertains to semiconductor structures containing ruggedsemiconductor materials, and pertains to methods of forming ruggedsemiconductor-containing surfaces.

BACKGROUND OF THE INVENTION

Rugged semiconductor surfaces are frequently utilized in applications inwhich it is desired to have an increased surface area. For instance,rugged semiconductor materials are frequently utilized as storage nodesin capacitor constructions.

The semiconductor of a rugged semiconductor material can comprise,consist essentially of, or consist of any element known to havesemiconductive properties. The semiconductor will frequently comprise,consist essentially of, or consist of silicon. In applications in whichthe semiconductor consists essentially of, or consists of silicon, therugged semiconductor material can be referred to as rugged silicon, andin exemplary applications can be hemispherical grain (HSG) silicon.

Although techniques are known for forming rugged semiconductor surfaces,there is a continuing need to develop improved methodologies forcontrolling the particular topography associated with a ruggedsemiconductor surface. In other words, there is a continuing need forcontrolling the ruggedness of the surfaces. Accordingly, it is desiredto develop improved methods for forming rugged semiconductor surfaces.

SUMMARY OF THE INVENTION

In one aspect, the invention encompasses a semiconductor structure. Suchstructure includes a stack comprising at least three semiconductorlayers over a substrate. Two of the three semiconductor layers areadjacent one another, and an interface layer is between the adjacentsemiconductor layers. The interface layer can have a thickness of lessthan or equal to about 10 Å, and can comprise insulative, semiconductiveor conductively-doped semiconductive materials. A bottom of the stack isconductively-doped semiconductor material, and a top of the stackcomprises a rugged semiconductor-containing surface.

In another aspect, the invention encompasses a method of forming arugged semiconductor-containing surface. A first semiconductor layer isformed over a substrate, and a second semiconductor layer is formed overthe first semiconductor layer. Subsequently, a third semiconductor layeris formed over the second semiconductor layer. Semiconductor-containingseeds are formed over the third semiconductor layer. The seeds areannealed to form the rugged semiconductor-containing surface. The first,second and third semiconductor layers are part of a common stack, andcan be together utilized within a storage node of a capacitorconstruction.

In another aspect, the invention encompasses a method of forming ruggedsilicon. Silicon-containing seeds are grown over a semiconductor layer.The growing of the seeds comprises two or more depositions of thesilicon of the seeds, with the depositions differing relative to oneanother in at least one process parameter. Such process parameter caninclude, for example, a relative time of the depositions, and/or arelative vacuum utilized during the depositions.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred embodiments of the invention are described below withreference to the following accompanying drawings.

FIG. 1 is a diagrammatic, cross-sectional view of a semiconductor waferfragment at a preliminary stage of an exemplary method of the presentinvention.

FIG. 2 is a view of the FIG. 1 wafer fragment shown at a processingstage subsequent to that of FIG. 1.

FIG. 3 is a view of the FIG. 1 wafer fragment shown at a processingstage subsequent to that of FIG. 2.

FIG. 4 is a view of a semiconductor wafer fragment shown at apreliminary processing stage in accordance with an exemplary secondembodiment of the present invention.

FIG. 5 is a diagrammatic, cross-sectional view of a semiconductor waferfragment illustrating an exemplary DRAM cell formed in accordance withan aspect of the present invention.

FIG. 6 is a diagrammatic view of a computer illustrating an exemplaryapplication of the present invention.

FIG. 7 is a block diagram showing particular features of the motherboardof the FIG. 6 computer.

FIG. 8 is a high-level block diagram of an electronic system accordingto an exemplary aspect of the present invention.

FIG. 9 is a simplified block diagram of an exemplary electronic systemaccording to an aspect of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

This disclosure of the invention is submitted in furtherance of theconstitutional purposes of the U.S. Patent Laws “to promote the progressof science and useful arts” (Article 1, Section 8).

As discussed in the “Background” section of this disclosure, it isdifficult to control the relative size and shape of topographicalfeatures when utilizing prior art processes to form rugged semiconductorsurfaces (such as, for example, hemispherical grain polysiliconsurfaces). One aspect of the present invention is to utilize pulsingprocesses to provide control of topographical features associated withrugged semiconductor materials. Such control can allow increased surfacearea to be accomplished, which can lead to improved devices. Forinstance, the increased surface area can be utilized in a storage nodeof a container capacitor, which can lead to higher capacitance for thestructure than would be obtained if prior art rugged semiconductorstructures were utilized.

In order to assist the reader in understanding the process of thepresent invention, a brief discussion of particular differences betweenan exemplary embodiment of the present invention and the prior art isprovided. A typical prior art process for forming HSG silicon is asfollows. Initially, doped polysilicon is provided. An undoped layer ofsmooth polysilicon is then formed over and physically against the dopedpolysilicon. Subsequently, the undoped silicon is exposed to a seedingprocess. The seeding is accomplished in one step, in that seedingmaterials are provided for an appropriate period of time, and under anappropriate vacuum to form the seeds as a single layer. Subsequently,the seeds and underlying silicon layers are annealed to form the ruggedsilicon. The seeds and undoped silicon can be doped during the annealingprocess by out-diffusion of dopant from the underlying doped silicon.Alternatively, and/or additionally, dopant can be implanted into theseeds and undoped silicon to conductively dope the seeds and underlyingundoped silicon. The dopant implanting can occur at any suitable timerelative to the annealing, including before or after the annealing.

In particular aspects, the present invention differs from the prior artprocesses in that multiple doped silicon layers can be providedutilizing a pulsed process, and/or multiple non-conductively-dopedsilicon layers can be provided in a pulsed process. The various layerscan differ from one another in the composition of semiconductormaterial. Also, if the various layers are conductively-doped layers, thelayers can differ from one another in the concentration, type and/orchemical constituency of the dopant materials. In particular aspects,interface layers can be provided between one or more of thepulse-deposited layers. The interface layers can be very thin (withexemplary interface layers being less than 10 Å thick, and in some casesbeing less than 5 Å thick). The interface layers can be utilized asbarriers to alleviate and/or prevent dopant migration between adjacentlayers during the seeding and/or annealing stages. Additionally, and/oralternatively, the interface layers can be utilized to prevent crossdiffusion of constituent materials of the various semiconductor layersduring the annealing and/or seeding.

The invention can also include a pulsed process for forming the seeds.Specifically, the seeds can be formed in multiple steps, with the stepsvarying from one another in one or more process parameters. Forinstance, a first layer of the seeds can be formed under a first vacuumcondition for a first deposition time, and subsequently a second seedlayer can be formed under a second vacuum condition which is differentthan the first, and for a second time which may also be different thanthe first. The different process parameters could also encompassutilization of different precursors, so that various layers of the seeddiffer in chemical constituency relative to one another.

The pulsing processes utilized in methodology of the present inventioncan change a bonding structure of an atom bonding network (Si—Si, Si—P,etc.), and can thus affect rugged semiconductor formation. Temperature,time, pressure, gas flow rate and/or other conditions can be changedduring formation of the various base semiconductor layers (eitherconductively-doped or undoped base layers), as well as during formationof the seeds. Variation of the various parameters can allow optimizationof rugged silicon shape, density and size to be achieved for aparticular application. Such can allow a rugged semiconductor materialto be formed having a larger surface area than prior art materials, andalso to be formed having topographical features which allow the surfaceto be better optimized for a particular application. For instance, arugged semiconductor surface formed in accordance with the presentinvention can be included within a container capacitor as a storagenode, and can allow a larger capacitance to be achieved from thecapacitor than could be achieved utilizing rugged semiconductormaterials formed in accordance with prior art methodologies.

Various exemplary aspects of the invention are described with referenceto FIGS. 1-3.

Referring initially to FIG. 1, a construction 10 is illustrated at apreliminary processing stage of an exemplary aspect of the presentinvention. Construction 10 comprises a substrate 12 which can be, forexample, a semiconductor substrate. To aid in interpretation of theclaims that follow, the terms “semiconductive substrate” and“semiconductor substrate” are defined to mean any constructioncomprising semiconductive material, including, but not limited to, bulksemiconductive materials such as a semiconductive wafer (either alone orin assemblies comprising other materials thereon), and semiconductivematerial layers (either alone or in assemblies comprising othermaterials). The term “substrate” refers to any supporting structure,including, but not limited to, the semiconductive substrates describedabove. Although substrate 12 is shown as a single mass, it is to beunderstood that the substrate can comprise numerous discrete materials.For instance, substrate 12 can comprise an insulative material overmonocrystalline silicon.

A stack 14 is formed over substrate 12. The exemplary stack comprises apair of conductively-doped semiconductor layers (16 and 18); a pair ofsemiconductor layers which are not conductively-doped (20 and 22); andan interface layer 24 between the upper conductively-doped layer 18 andthe lower layer 20 which is not conductively-doped.

The shown stack 14 can be considered to comprise at least threesemiconductor layers, and in the shown aspect comprises foursemiconductor layers. The various layers can be considered to be afirst, second, third and fourth semiconductor layer, which are formedover one another. The layers 16, 18, 20, 22 and 24 which are part of thecommon stack 14 can be ultimately incorporated into a single circuitdevice. For instance, the layers can be incorporated into a capacitorand comprised by a storage node of the capacitor.

The semiconductor material of layers 16, 18, 20 and 22 can comprise anysuitable semiconductive element, including, for example, one or both ofsilicon and germanium.

Conductively-doped layers 16 and 18 differ from one another, and can bedistinguished from one another. The difference between layers 16 and 18can be anything which enables the layers to be distinguished from oneanother, including, for example, (1) one or more of a relative dopantconcentration between the layers; (2) a majority dopant type within thelayers (for instance, one of the layers can be majority p-type and theother can be majority n-type); (3) the chemical composition of thedopant (for instance, both layers can comprise the same majority dopanttype, but can differ from one another in terms of the actual dopantutilized, for instance, if both are n-type majority doped, one canpredominately comprise phosphorous and the other predominately comprisearsenic); and (4) the chemical composition of the semiconductor (forinstance, one of the layers can comprise silicon/germanium while theother consists of silicon, or both layers can comprise silicon/germaniumwith the relative amount of germanium differing between the layers).

Layers 16 and 18 can be formed in what can be considered a pulsedprocess, with layer 16 being first deposited, then one or more processparameters being changed and layer 18 being subsequently deposited.Layers 16 and 18 can be deposited in the same reaction chamber, andwithin a continuous process occurring without breaking vacuum to thedeposition chamber. Layers 16 and 18 can be formed by atomic layerdeposition (ALD) processes, chemical vapor deposition process (CVD), orcombinations of these and/or other suitable processes. Layers 16 and 18can be formed to thickness of from about 40 Å to about 1000 Å, and intypical processing each will have a thickness of about 40 Å.

Layers 20 and 22 can differ from one another in any property thatenables layers 20 and 22 to be distinguished from one another. Forinstance, layers 20 and 22 can differ from one another in terms of thesemiconductor composition of the layers. One of the layers can comprisesilicon/germanium and the other can consist of silicon. Alternatively,both of the layers can comprise silicon/germanium, with the relativeamount of germanium differing in one layer relative to the other. Layers20 and 22 can comprise thicknesses of from about 40 Å to about 1000 Å,and typically each will have a thickness of about 40 Å. Layers 20 and 22can be formed by any suitable process, including ALD, CVD and/or otherprocesses.

It is noted that layers 20 and 22 are referred to as being notconductively-doped, and such term should not be understood to mean thatthe layers 20 and 22 contain absolutely no dopant. Rather, a layer whichis not conductively-doped is, as is understood in the art, a layer whichcan contain some dopant, but which contains too little dopant to beconsidered electrically conductive.

In the discussion above, it should be understood that the semiconductormaterial of layers 16, 18, 20 and 22 can comprise any element, orcombination of elements known to be semiconductive, and in particularaspects can comprise, consist essentially of, or consist of silicon; orin other exemplary aspects can comprise, consist essentially of, orconsist of silicon/germanium.

Interface layer 24 separates doped layer 18 from the adjacent layer 20that is not conductively-doped, and in the shown aspect of the inventionis the only material between layers 18 and 20. Interface layer 24 cancomprise silicon dioxide, silicon nitride, silicon oxynitride, silicon,germanium, and/or silicon/germanium. If layer 24 comprises asemiconductor, the semiconductor can be, in particular aspects,conductively-doped.

In some applications, layer 24 can consist essentially of, or consist ofan insulative material which can function as a dopant barrier betweenconductively-doped layer 18 and the non-conductively-doped layer 20, andin such aspects can comprise, consist essentially of, or consist ofsilicon dioxide, silicon nitride or silicon oxynitride.

Layer 24 can be formed over layer 18 by, for example, oxidation ofsemiconductor material of layer 18, nitridation of the semiconductormaterial layer 18, or by ALD or CVD of a desired material over layer 18.

In particular aspects, layer 24 has a thickness of less than 10 Å, andmore preferably less than 5 Å. A reason for keeping layer 24 thin is sothat the layer does not subsequently impede conductivity between layers18 and 20 in a device ultimately formed to comprise stack 14.Specifically, if stack 14 is ultimately utilized to form a ruggedsemiconductor surface, it can be desired to subsequently dope layers 20and 22 so that an entirety of stack 14 is conductively-doped. It canalso be desired to have relatively unimpeded electrical conductance fromlayer 16 to layer 22. Accordingly, it can be desired to have layer 24formed thin enough so that the layer does not ultimately impedeelectrical conductance between layers 16 and 22 in a circuit deviceincorporating stack 14.

A reason for utilizing interface layer 24 at initial processing stagesof forming rugged silicon from stack 14 is that it can be difficult tocontrol fabrication of a rugged semiconductor if dopant migrates fromthe lower doped portions of the stack to the upper portions of the stackduring fabrication of the rugged surface. Specifically, the dopant caninterfere with the fabrication of the rugged surface, and ultimatelyaffect the resulting topography of the rugged surface.

One solution which would appear to avoid migration of dopant into layers20 and 22 without utilization of interface layer 24 is to simply notprovide any conductively-doped layers within stack 14. However, suchsolution is typically not practical in that a rugged semiconductorformed utilizing layer 14 is usually intended to be a conductively-dopedmaterial throughout an entirety of its thickness (for instance, therugged material will frequently be utilized as a storage node of acapacitor), and it is generally impractical to implant aconductivity-enhancing dopant through an entire thickness of the ruggedmaterial. Accordingly, the application of the rugged material typicallystarts with a lower portion of the stack utilized for forming the ruggedmaterial being conductively-doped so that the lower portion of therugged semiconductive material later formed from the stack will have theappropriate conductivity doping without need for an implant to penetratethe entire thickness of the stack.

In the shown application, the conductively-doped portion of stack 14 isapproximately the lower half of the stack. It is to be understood,however, that in other applications the conductively-doped portion canbe less than half the thickness of the stack, and in yet otherapplications the conductively-doped portion can be more than half thethickness of the stack.

Although interface layer 24 is shown between a conductively-doped layer18 and a layer 20 which is not conductively-doped, it is to beunderstood that layer 24 can be formed between conductively-doped layersadditionally and/or alternatively to its formation between aconductively-doped layer and a layer not conductively-doped; and alsothat layer 24 can be formed between a pair of semiconductor layers whichare not conductively-doped additionally and/or alternatively to itsformation between a conductively-doped layer and a layer which is notconductively-doped. An advantage to forming an interface layer between apair of layers which are conductively-doped is that the interface layercan prevent dopant migration between the conductively-doped layers tothe extent that the layers comprise dopants having different chemicalconstituencies relative to one another. Also, even if layer 24 is not adopant barrier layer, the layer can be utilized to modify a behavior ofstack 14 during formation of rugged silicon, which can provideadditional control of the fabrication of the rugged silicon.

An advantage to forming interface layer 24 between a pair ofsemiconductor layers which are not conductively-doped is that theinterface layer can be a dopant barrier layer which allows the lower ofthe non-conductively-doped layers to become conductively-doped throughout-diffusion from conductively-doped layers below suchnon-conductively-doped layer, while preventing out-diffusion into theupper non-conductively-doped layer. Alternatively, if layer 24 is not adopant barrier layer, there can still be advantages to utilizing suchlayer between the non-conductively-doped layers in that layer 24 canmodify behavior of stack 14 during fabrication of rugged semiconductormaterials, which can provide additional control of the fabrication ofthe semiconductor materials.

It is emphasized that although the invention is described as growing astack upwardly, with lower portions of the stack being conductive andupper portions of the stack being non-conductive, the relativeorientations of the non-conductive portions and conductively-dopedportions can be changed depending on the orientation of the substrate.Accordingly, the non-conductively-doped portions can be formed laterallyoutward of conductively-doped portions, or even downwardly ofconductively-doped portions in various aspects of the invention.Further, the directional terms upwardly, downwardly, and laterallyoutwardly are, unless specified otherwise, defined relative to thesubstrate itself, rather than relative to an outside observer.Accordingly, a layer which is formed over another in the context of thisinvention, may actually appear to be formed below the other to anobserver, depending on the frame of reference of the observer to thesubstrate.

Although stack 14 is shown to comprise conductively-doped semiconductormaterials adjacent one another in one portion of the stack, andnon-conductively-doped portions adjacent one another in another portionof the stack, it is to be understood that the conductively-dopedportions and non-conductively-doped portions can alternate with oneanother within the stack in various aspects of the invention. However, aportion of stack 14 most proximate to the supporting substrate 12 willtypically be conductively-doped, and the portion having an exposedsurface will typically be non-conductively-doped. Accordingly, the shownlowermost portion 16 is conductively-doped, and the shown uppermostportion 22 is not conductively-doped.

The total number of semiconductor layers 16, 18, 20 and 22 utilized instack 14 (i.e. the layers typically having a thickness of from 40 Å to1000 Å) will typically be from about 4 to about 10, with from about 2 toabout 5 conductively-doped layers typically being utilized, and fromabout 2 to about 5 non-conductively-doped layers typically beingutilized. The total number of interface layers can therefore typicallybe from about 1 to about 9.

Referring to FIG. 2, seeds 31, 33, 35, and 37 are formed over an exposedupper surface of non-conductively-doped semiconductor layer 22, and inthe shown embodiment are formed physically against the upper surface oflayer 22. Since layers 16, 18 and 20 are covered by layer 22, the seedsare not formed against any surfaces of layers 16, 18 and 20. Seeds 31,33, 35 and 37 comprise semiconductor material, and in particular aspectscan comprise, consist essentially of, or consist of silicon. The seedscomprise multiple layers 32, 34 and 36. The various layers aredistinguishable from one another in at least one property. Such propertycan be a physical parameter (such as, for example, density), and/or achemical parameter (such as, for example, composition). The variouslayers of the seeds are formed by growing the seeds in multipledepositions, with the depositions differing relative to one another inat least one process parameter. In the shown exemplary aspect of theinvention, the seeds have been grown with three different depositions toform three different layers. However, it is to be understood that theseeds can be grown generally with two or more depositions.

The different process parameter utilized in growing one layer of theseeds relative to another can include, for example, a relative time ofthe deposition, a relative vacuum utilized during the deposition, and/ora change in the composition of precursor utilized in the deposition. Achange in vacuum and/or deposition time can result in a change ofdensity of a layer relative to previously-deposited layers, and a changein precursor composition can result in a change of the chemicalcomposition of the layer relative to previously deposited layers. Thevacuum utilized in forming layers 32, 34 and 36 will typically be fromabout 1 mTorr to about 50 mTorr and a deposition time will typically befrom about 1 minute to about 5 minutes. The precursor can be asilicon-containing material (such as silane), a germanium-containingmaterial, or a combination of silicon-containing materials andgermanium-containing materials. The total number of layers formed forgiven seed will typically be formed within a total time of about 15minutes.

The utilization of multiple different layers within the seeds can enablecontrol of shape and density of the seeds, which ultimately enablesadditional control of the topography of a rugged semiconductor surfaceformed utilizing the seeds.

After seeds 31, 33, 35 and 37 are formed, construction 10 is subjectedto an appropriate anneal to form a rugged semiconductor surface from theseeds. Such anneal will typically be conducted for a time of about 30minutes at a temperature of from about 550° C. to about 610° C., underan appropriate inert gas (such as, for example, N₂, He, or H₂). Also,seeds 31, 33, 35 and 37, together with non-conductively doped layers 20and 22, will be subjected to an implant of conductivity-enhancing dopantto convert layers 20, 22, 32, 34 and 36 to electrically conductivematerials. The doping can be conducted before or after the anneal.

FIG. 3 shows construction 10 after an appropriate anneal, and after thedoping of layers 20, 22, 32, 34 and 36. Seeds 31, 33, 35 and 36,together with stack 14, form a rugged semiconductor material 38 having asurface topography 40 which extends across exposed portions of layer 22and exposed portions of layer 36. It is to be understood, however, thatin particular embodiments seeds 31, 33, 35 and 36 can grow to contactone another, and accordingly there would not exposed portions of layer22 along the topographical surface.

Layers 16, 18, 20, 22, 24, 32, 34 and 36 are shown to remaindistinguishable from one another in the final construction of FIG. 3. Insome aspects of the invention, diffusion between various of the layerscan cause differences between the layers to be reduced, or eveneliminated, such that various of the layers are no longerdistinguishable relative to one another at the final stage of theprocessing shown in FIG. 3. In other aspects, the differences can remainrelative to at least some of the layers, so that at least some of thelayers are distinguishable relative to one another at the processingstage of FIG. 3. Regardless, the utilization of multiple differentlayers in the processing sequence of FIGS. 1-3 can provide control ofthe surface topography of a rugged semiconductor material that does notexist in prior art processes.

FIG. 4 shows a construction 50 at a processing stage similar to thatdescribed previously with reference to FIG. 1, and in referring toconstruction 50 identical numbering will be utilized as was used abovein describing construction 10 of FIG. 1, where appropriate. Construction50 comprises a substrate 12, and a stack 54 of various layers oversubstrate 12. The layers within stack 54 are labeled as 56, 58, 60, 62,64, 66, 68, 70, 72, 74, 76, 78 and 80. Layers 56, 60, 64 and 72 areconductively-doped semiconductor layers, which can compriseconstructions identical to those described previously with reference tolayers 16 and 18 of FIG. 1. Layers 58, 68, 76 and 80 are semiconductorlayers which are not conductively-doped, and can comprise constructionsidentical to those described above with reference to layers 20 and 22 ofFIG. 1. Layers 62, 66, 70, 74 and 78 are interface layers, and cancomprise constructions identical to those described previously withreference to layer 24 of FIG. 1.

FIG. 4 illustrates that a non-conductively-doped semiconductor layer canbe provided between a pair of conductively-doped semiconductor layers inparticular aspects of the invention (for instance, layer 58 is betweenlayers 56 and 60). FIG. 4 also illustrates that a conductively-dopedsemiconductor layer can be provided between a pair ofnon-conductively-doped semiconductor materials in particular aspects ofthe invention, (for instance, layer 72 is between layers 68 and 76).Additionally, FIG. 4 illustrates that interface materials can beprovided between a pair of conductively-doped semiconductor layers (forinstance, layer 62 is between layers 64 and 66), and that an interfacematerial can be provided between a pair of non-conductively-dopedsemiconductor layers (for instance, interface layer 78 is between layers76 and 80).

Stack 54 can be subjected to processing similar to that described abovewith reference to FIGS. 2 and 3 to form a rugged semiconductor materialcomprising the various layers of stack 54.

In exemplary aspects of the invention, the interface layers can beconsidered to separate adjacent semiconductor layers. In accordance withthe above-described exemplary constructions of the semiconductor layersand interface layer, it is to be understood that numerous combinationsof interface layers and semiconductor layers can be utilized inaccordance with various aspects of the invention. For instance, theadjacent semiconductor layers can consist of silicon or doped siliconand the interface layer can comprise, consist essentially of, or consistof Si/Ge. Also, the adjacent semiconductor layers can beconductively-doped, and the interface layer can be a semiconductormaterial which is not conductively-doped. Such non-conductively-dopedinterface semiconductor material can comprise, for example, germaniumand/or silicon.

FIG. 5 illustrates a semiconductor construction 100 comprising therugged semiconductor material 38 of FIG. 3 incorporated into a DRAM cell102.

DRAM cell 102 comprises a substrate 104. Substrate 104 can comprise, forexample, lightly-doped monocrystalline silicon. A transistor device 106is associated with substrate 104 and comprises a transistor gate 108separated from substrate 104 by a suitable insulative material 110, anda pair of source/drain regions 112 extending into substrate 104.Although transistor gate 108 is shown to be homogenously conductive, itis to be understood that the gate can, in accordance with conventionalpractices, comprise multiple layers of conductive materials, and alsothat the gate can comprise an insulative cap (not shown) over a top ofthe gate. Sidewall spacers 114 are shown adjacent sidewalls of gate 108.

A conductive pedestal 116 extends to electrically contact one of thesource/drain regions 112.

An insulative material 118 is over gate 108, and an opening 120 extendsthrough insulative material 118 to conductive pedestal 116.

Rugged semiconductor material 38 is formed within opening 120 to definea storage node of a container capacitor construction.

A dielectric material 122 extends within opening 120 and conformallyalong the roughened surface 40 of rugged semiconductor construction 38.

A second capacitor electrode 124 is provided over dielectric material122 and separated from the first capacitor electrode (i.e. the storagenode comprising construction 38) by the dielectric material 122.

Dielectric material 122 can comprise any suitable dielectric material,including, for example, silicon nitride, silicon dioxide, or varioushigh-k materials. Capacitor electrode 124 can comprise any suitableelectrically conductive material, including, for example, variousmetals, metal compounds, and/or conductively-doped semiconductormaterials.

Storage node 38, dielectric material 122 and capacitor electrode 124together define a capacitor construction 126 which is in electricalconnection with one of the source/drains of transistor device 106. Theother of the source/drains 112 is in electrical connection with abitline 128.

Utilization of methodology of the present invention enables theruggedness of surface 40 to be better controlled than it could beutilizing prior art processes. Such can enable capacitor construction126 to have a higher capacitance than a capacitor formed in the sameopening utilizing a storage node formed in accordance with prior artprocesses. As discussed previously, surface 40 can consist of a surfaceof the seeds 31, 33, 35 and 37 described previously with reference toFIGS. 2 and 3, or can comprise surfaces of the seeds together with asurface of semiconductor material 22. In either event, rugged surface 40can comprise silicon, consist essentially of silicon, or consist ofsilicon.

A circuit device comprising rugged semiconductor material formed inaccordance with methodology of the present invention can be utilized innumerous assemblies, including, for example, computer systems and otherelectronic systems.

FIG. 6 illustrates generally, by way of example, but not by way oflimitation, an embodiment of a computer system 400 according to anaspect of the present invention. Computer system 400 includes a monitor401 or other communication output device, a keyboard 402 or othercommunication input device, and a motherboard 404. Motherboard 404 cancarry a microprocessor 406 or other data processing unit, and at leastone memory device 408. Memory device 408 can comprise various aspects ofthe invention described above, including, for example, the DRAM unitcell described with reference to FIG. 5. Memory device 408 can comprisean array of memory cells, and such array can be coupled with addressingcircuitry for accessing individual memory cells in the array. Further,the memory cell array can be coupled to a read circuit for reading datafrom the memory cells. The addressing and read circuitry can be utilizedfor conveying information between memory device 408 and processor 406.Such is illustrated in the block diagram of the motherboard 404 shown inFIG. 7. In such block diagram, the addressing circuitry is illustratedas 410 and the read circuitry is illustrated as 412.

In particular aspects of the invention, memory device 408 can correspondto a memory module. For example, single in-line memory modules (SIMMs)and dual in-line memory modules (DIMMs) may be used in theimplementation which utilize the teachings of the present invention. Thememory device can be incorporated into any of a variety of designs whichprovide different methods of reading from and writing to memory cells ofthe device. One such method is the page mode operation. Page modeoperations in a DRAM are defined by the method of accessing a row of amemory cell arrays and randomly accessing different columns of thearray. Data stored at the row and column intersection can be read andoutput while that column is accessed.

An alternate type of device is the extended data output (EDO) memorywhich allows data stored at a memory array address to be available asoutput after the addressed column has been closed. This memory canincrease some communication speeds by allowing shorter access signalswithout reducing the time in which memory output data is available on amemory bus. Other alternative types of devices include SDRAM, DDR SDRAM,SLDRAM, VRAM and Direct RDRAM, as well as others such as SRAM or Flashmemories.

FIG. 8 illustrates a simplified block diagram of a high-levelorganization of various embodiments of an exemplary electronic system700 of the present invention. System 700 can correspond to, for example,a computer system, a process control system, or any other system thatemploys a processor and associated memory. Electronic system 700 hasfunctional elements, including a processor or arithmetic/logic unit(ALU) 702, a control unit 704, a memory device unit 706 and aninput/output (I/O) device 708. Generally, electronic system 700 willhave a native set of instructions that specify operations to beperformed on data by the processor 702 and other interactions betweenthe processor 702, the memory device unit 706 and the I/O devices 708.The control unit 704 coordinates all operations of the processor 702,the memory device 706 and the I/O devices 708 by continuously cyclingthrough a set of operations that cause instructions to be fetched fromthe memory device 706 and executed. In various embodiments, the memorydevice 706 includes, but is not limited to, random access memory (RAM)devices, read-only memory (ROM) devices, and peripheral devices such asa floppy disk drive and a compact disk CD-ROM drive. One of ordinaryskill in the art will understand, upon reading and comprehending thisdisclosure, that any of the illustrated electrical components arecapable of being fabricated to include DRAM cells in accordance withvarious aspects of the present invention.

FIG. 9 is a simplified block diagram of a high-level organization ofvarious embodiments of an exemplary electronic system 800. The system800 includes a memory device 802 that has an array of memory cells 804,address decoder 806, row access circuitry 808, column access circuitry810, read/write control circuitry 812 for controlling operations, andinput/output circuitry 814. The memory device 802 further includes powercircuitry 816, and sensors 820, such as current sensors for determiningwhether a memory cell is in a low-threshold conducting state or in ahigh-threshold non-conducting state. The illustrated power circuitry 816includes power supply circuitry 880, circuitry 882 for providing areference voltage, circuitry 884 for providing the first wordline withpulses, circuitry 886 for providing the second wordline with pulses, andcircuitry 888 for providing the bitline with pulses. The system 800 alsoincludes a processor 822, or memory controller for memory accessing.

The memory device 802 receives control signals 824 from the processor822 over wiring or metallization lines. The memory device 802 is used tostore data which is accessed via I/O lines. It will be appreciated bythose skilled in the art that additional circuitry and control signalscan be provided, and that the memory device 802 has been simplified tohelp focus on the invention. At least one of the processor 822 or memorydevice 802 can include a DRAM cell of the type described previously inthis disclosure.

The various illustrated systems of this disclosure are intended toprovide a general understanding of various applications for thecircuitry and structures of the present invention, and are not intendedto serve as a complete description of all the elements and features ofan electronic system using memory cells in accordance with aspects ofthe present invention. One of the ordinary skill in the art willunderstand that the various electronic systems can be fabricated insingle-package processing units, or even on a single semiconductor chip,in order to reduce the communication time between the processor and thememory device(s).

Applications for memory cells can include electronic systems for use inmemory modules, device drivers, power modules, communication modems,processor modules, and application-specific modules, and may includemultilayer, multichip modules. Such circuitry can further be asubcomponent of a variety of electronic systems, such as a clock, atelevision, a cell phone, a personal computer, an automobile, anindustrial control system, an aircraft, and others.

In compliance with the statute, the invention has been described inlanguage more or less specific as to structural and methodical features.It is to be understood, however, that the invention is not limited tothe specific features shown and described, since the means hereindisclosed comprise preferred forms of putting the invention into effect.The invention is, therefore, claimed in any of its forms ormodifications within the proper scope of the appended claimsappropriately interpreted in accordance with the doctrine ofequivalents.

1-82. (canceled)
 83. A DRAM cell, comprising: a capacitor which includesa first capacitor electrode, a second capacitor electrode, and at leastone dielectric material between the first and second capacitorelectrodes; one of the first and second capacitor electrodes including astack comprising at least three semiconductor layers, two of the threesemiconductor layers being adjacent one another; a bottom of the stackbeing conductively-doped semiconductor material and a top of the stackcomprising a rugged semiconductor-containing surface, there being atleast one interface layer in the stack, the interface layer beingbetween the adjacent semiconductor layers; and a transistor having asource/drain region electrically coupled with one of the first andsecond capacitor electrodes.
 84. (canceled)
 85. The DRAM cell of claim83 wherein the semiconductor of the rugged semiconductor-containingsurface comprises silicon.
 86. The DRAM cell of claim 83 wherein theinterface layer has a thickness of less than or equal to about 10 Å. 87.The DRAM cell of claim 83 wherein the interface layer comprises silicondioxide.
 88. The DRAM cell of claim 83 wherein the interface layercomprises silicon nitride.
 90. The DRAM cell of claim 83 wherein theadjacent semiconductor layers consist of silicon or doped silicon, andthe interface layer comprises Si/Ge.
 91. The DRAM cell of claim 83wherein the transistor source/drain region is electrically connected tothe capacitor electrode which comprises said at least threesemiconductor layers.